It has already been proposed to make tennis-racket frames from various metals or alloys, notably from aluminum, magnesium or beryllium which have a low ratio of weight to stiffness. It has also been suggested (see British Pat. No. 1,099,400) to make the frames of smaller rackets, such as those used for badminton, of solid titanium.
The known metallic tennis-racket frames generally have a hollow profile indented to form an external groove on the frame which accommodates the strings. The groove bottom and the opposite profile wall, defining the inner frame periphery, have aligned perforations through which the strings pass, adjoining perforations being bridged by short string sections within the groove. The impact of a ball upon the strings tensions the latter, thus exerting a generally radial stress upon the profile section constituting the groove bottom; to absorb these stresses, the profile is frequently provided with internal reinforcing webs. A profile of this type is virtually nondeformable in the plane of the strings so that the striking force of the ball must be absorbed by the elasticity of the strings themselves and by the resiliency of the frame in the direction of impact, i.e. perpendicular to the string plane or face of the racket. Such a perpendicular deflection of the racket is undesirable since it diminishes the precision with which a player can hit the ball in a desired direction. Gut strings, which have the requisite elasticity, are expensive and have only a limited service life.
With rackets using strings of less elastic material, e.g. synthetic resin such as nylon, their resiliency may be increased by extraneous means such as coil springs connecting them with the frame. Reference may be made in this connection to my German published patent application Nos. 2,116,920 and 2,225,595.